1. Field of the Invention
The present invention relates to a developer regulating member for regulating an amount of developer carried on a developer carrying member, and a developing apparatus having this developer regulating member. Those are preferably used for a copier, a printer, an image forming apparatus such as a facsimile apparatus, or a process cartridge that can be detachably attached to an image forming apparatus main body.
2. Related Background Art
Conventionally, in an image forming apparatus such as a copier, a printer, or a facsimile apparatus provided with a function for forming an image on a recording medium, an electrostatic latent image formed on an electrostatic latent image bearing member is visualized as a developer image (toner image) using a developer by a developing apparatus.
As such a developing apparatus, for example, a dry one-component contact developing apparatus has been proposed and put to practical use. In this case, an electrostatic latent image is often developed by pushing a developer carrying member carrying a developer, which rotates in the same manner as a rotating electrostatic latent image bearing member, against or bringing it into contact with the electrostatic latent image bearing member with an appropriate relative peripheral velocity difference. In addition, in this case, there are many advantages in that, for example, a magnetic material is unnecessary so that simplification and miniaturization of the apparatus are easy, and the apparatus can be applied to a full-color image forming apparatus by using a nonmagnetic toner.
In a contact development system, a developing roller having elasticity and electric conductivity is often used as a developer carrying member. That is, since an electrostatic latent image is developed by pushing the developer carrying member against or bringing it into contact with an electrostatic latent image bearing member, in particular, in the case in which the electrostatic latent image bearing member is a rigid body, the developing roller is constituted by an elastic body in order to avoid damage to the electrostatic latent image bearing member.
In addition, it is also possible to provide a conductive layer on a surface of the developing roller or in the vicinity of the surface to apply a developing bias to the developing roller.
Moreover, in general, for the purpose of imparting an electric charge to a toner and forming a uniform thin toner layer, a developing blade is abutted against the developer carrying member as a developer regulating member. In this case, it is possible to use an elastic blade that is constituted by a thin metal plate having rubber or spring elasticity, as the developing blade.
The structure of a conventional developing apparatus will be described with reference to Fig. The developing apparatus 5 includes a developer container 56 for containing a developer 55. A developer carrying member 51 is provided in an opening part of the developer container 56, which is opposed to an electrostatic latent image bearing member 11 of the developing apparatus, with a developing part thereof exposed.
A developing roller 51 serving as the developer carrying member is an elastic roller having electric conductivity which has silicon rubber as a base layer and is coated with acrylic urethane rubber as a surface layer. The developing roller 51 is driven to rotate in a direction of arrow A′.
A developing blade 53 of a thin metal plate serving as a developer regulating member is provided in the developer container 56 containing the developer 55. The developing blade 53 is supported in a supported part thereof by a blade support metal sheet 52, and the vicinity of its tip on the free end side thereof is abutted against an external peripheral surface of the developing roller 51 so as to be in surface contact with the external peripheral surface.
Moreover, in the developer container 56, a developer supply roller (supply roller) 54 having elasticity abuts against the developing roller 51 and is driven to rotate in a direction of arrow B′ which is counter to the rotating direction A′ of the developing roller 51. The supply roller 54 is a sponge roller and is provided further on the upstream side of the rotating direction A′ of the developing roller 51 than the developing blade 53 for the purpose of supplying the developer 55 to the developing roller 51 and removing the developer 55 which is not used for development and remains on the developing roller 51.
The developer 55 is a nonmagnetic one-component developer containing a nonmagnetic toner. The developer 55 is externally added with an appropriate amount of hydrophobic silica for the purpose of improving toner charging property and transfer efficiency thereof.
The developer 55 is drawn up to the developing roller 51 by the supply roller 54, and the developing roller 51 rotates to carry the developer 55 to a developing portion opposed to the electrostatic latent image bearing member 11. In the course of carrying the developer 55, the developing blade 53 removes excess developer 55 on the developing roller 51, whereby an amount of developer 55 on the developing roller 51, that is, the developer layer thickness, is regulated.
In the developing apparatus with the above-mentioned structure, a thin layer of the nonmagnetic developer 55 can be formed satisfactorily on the developing roller 51, and an electrostatic latent image on the electrostatic latent image bearing member 11 can be developed satisfactorily.
However, in the prior art as described above, the developing roller 51 serving as a developer carrying member is an elastic roller having elasticity. In the case in which the developing roller 51 is abutted against the developing blade 53 serving as a developer regulating member for a long period of time, deformation of the developing roller 51 occurs in the abutment portion between the developing roller 51 and the developing blade 53, so that a developer 55 is not coated uniformly on the developing roller 51. Therefore, there is a problem in that a sharp line of high density appears in the formed image, that is, so-called developing roller set image failure occurs at a rotation period of the developing roller 51.